Objective: To determine whether patients in whom myositis develops after they receive silicone breast implants have distinct clinical, serologic, and/or immunogenetic features compared with patients with myositis who do not have silicone implants.
Methods: A preliminary case series study was followed by a larger, independent, matched case-control study to evaluate women in whom myositis developed after they received silicone implants (MASI patients) compared with healthy women with silicone implants and women with myositis but without silicone implants (idiopathic inflammatory myopathy; IIM patients).
Results: In a preliminary study, 11 MASI patients differed from 76 IIM patients in having an increased frequency of HLA-DQA1*0102 (odds ratio [OR] 9.8, 95% confidence interval [95% CI] 1.77-96.79) and decreased frequencies of the myositis-associated risk factor DRB1*0301 (OR 0.1 [95% CI 0.002-0.63]) and its linked allele DQA1*0501 (OR 0.2 [95% CI 0.02-0.87]). A subsequent independent, matched case-control study revealed that although clinical features and autoantibodies did not differ significantly between the MASI and IIM groups, MASI patients again had decreased frequencies of DRB1*0301 (OR 0.2 [95% CI 0.07-0.72]) and DQA1*0501 (OR 0.2 [95% CI 0.08-0.84]) compared with IIM patients. Additional comparisons between MASI patients from both studies combined (n = 37) and a larger population of IIM patients (n = 453) suggested that HLA-DQA1*0102 may be uniquely associated with MASI (OR 2.6 [95% CI 1.25-5.46]).
Conclusion: Women in whom inflammatory myopathy develops after they receive silicone implants constitute an immunogenetically distinct group of patients with myositis. These and other data suggest that autoimmune diseases as now defined may consist of multiple distinct entities, each of which is characterized by different genes and environmental exposures.